In day to day tasks duals ARE better than quads hands down. You'll find VERY little difference between a quad and a dual core in running ms office, IE, and msn.sure, i cant argue that.
but that doestn mean that dual's are better than quads, or that quads have no use. and for an extra 20 bucks, at least they have it so if they ever figure out what it can do, they can do it.
If you fold, do heavy video or audio editing then yes it will work.
But this person asking is probably the person in group one and might as well save money where he can.